Electromechanical joining modules are electric motors which apply a linearly directed force onto a joining body by means of a tappet. Joining modules for assembly processes in which positive connections are produced are disseminated in particular. A joining module of this type is known for example from DE 19721072. This document does not discuss force measurements, however.
Joining modules of this type sometimes have force measuring apparatuses which measure force applied by the joining module onto a joining body. Measurement data captured in this manner are used for controlling the processes and/or for quality monitoring.
In the known joining modules, the force is for the most part detected in the housing of the joining module. In this case, the precision is limited due to the bearing friction, force shunts and also the sluggish mass of the moved parts. Alternatively, a force sensor can be integrated on the joining body. The cable connection to the force sensor is mechanically complex however and susceptible to faults and the lifetime of this cable connection is severely limited.
A tool for shaping, stamping and injection moulding technology, in which a force sensor is embedded in the functional surface of the tool, is known from EP 1057586. This is suitable for determining wear parameters on the tool, but not for measuring the force when joining as a whole. To this end, it should especially be avoided that the sensor is part of the functional surface, in order to prevent measurement errors due to local inhomogeneities. In addition, this document does not describe any actuator technology through which the tool moves and through which force is applied onto the tool. Thus, how the measurement data are transmitted from a joining body to a stator moving linearly thereto is also not described.
In DE 10251387, a press device, which has a torque sensor, is described. For this, the movement between the moveable part and the stationary part is a rotation, as a result of which the distance between both components remains virtually constant. This is a typical joining module as has been known for a long time. The force on the tool is determined using the torque sensor indirectly via the spindle pitch. Unknown variable friction forces of the spindle lead to relatively large measurement errors. As the sensor does not move translationally, a telemetric transmission of the measurement data is not a problem.